Preparation process of a flame retardant composition made from brominated bismuth and/or antimony compounds complexed with melamine and composition obtained thereby

ABSTRACT

Described herein is a preparation process of a flame retardant composition made from brominated bismuth and/or antimony compounds complexed with melamine, in which melamine, at least one between the bismuth carbonate and antimony sesquioxide, hydrobromic acid in aqueous solution are placed in contact with each other so as to trigger chemical reactions which lead to the formation of a complex of brominated bismuth or brominated antimony with melamine and melamine bromohydrate. The reagents are placed in contact in the presence of at least one reaction carrier defined by at least one compound chosen from the group consisting of melamine, melamine phosphate, melamine polyphosphate, ammonium phosphate, ammonium polyphosphate, triphenyl-phosphate, graphite, silica, lignin, coke and compounds containing triazine rings condensed or linked by —NH groups. The reaction carrier is not involved in the reactions. There are no polymeric compounds in quantities such as to create a polymer matrix. The reagents being introduced into the reactor in an amount defined by the stoichiometric ratios of said reactions. The reaction carrier is introduced into the reactor in an amount defined with respect to the total weight of the reagents so that it can perform a modulator function.

RELATED APPLICATION

This is a divisional application of U.S. Ser. No. 15/517,355 filed Apr.6, 2017, now allowed, which is a national stage application filed under35 U.S.C. § 371 of international application PCT/IB2015/055691, filedunder the authority of the Patent Cooperation Treaty on Jul. 28, 2015,published; which claims the benefit of European Patent Application No.14425136.0, filed on Oct. 27, 2014. The entire disclosures of all theaforementioned applications are expressly incorporated herein byreference for all purposes.

FIELD OF APPLICATION

The present invention relates to a preparation process of a flameretardant composition made from brominated bismuth and/or antimonycompounds complexed with melamine and a composition obtained by suchprocess.

STATE OF THE ART

Bismuth/antimony bromide complexes with amines of various kinds, used asflame retardants, are known in the state of the art.

Such complexes suffer from the technical problems which typicallyafflict brominated organic compounds. In addition to the well-knownenvironmental aspects the corrosiveness resulting from the tendency torelease bromine or hydrogen bromide should be mentioned. The use of suchcompounds thus requires careful control of the intrinsic acidity of suchadditives (which may for example cause corrosion of equipment: extruderscrews, dies, presses, etc. . . . ). Moreover, the tendency todecomposition of such brominated compounds reduces theself-estinguishing properties of the material incorporating them. Thisrequires an increase in the effective amount of fire retardant in thedosing phase.

The U.S. Pat. No. 4,798,857 describes brominated or chlorinatedcompounds of bismuth or antimony complexed with amines of various kinds,having a good flame retardant action on thermoplastic polymers. Suchcomplexes have the general formula R (MEX₃)_(y) where R is an amineselected from the group consisting of dicyanamide, guanamine,2-guanidinobenzimidazole, melamine, isophorone diamine, piperazine,optionally substituted with an alkyl, aryl or acyl group, and compoundscontaining from 2 to 9 triazine rings condensed or linked to each otherby at least one —NH— group; Me is bismuth or antimony; X is chlorine orbromide; and y is a number between 0.3 and 4. These are pure,stoichiometrically defined complexes. Given the strictness of thestoichiometric formula the possibility of varying the content and the“type” of bromine or chlorine present, where required, is notcontemplated. The preparation process of the complexes described in U.S.Pat. No. 4,798,857 in particular provides for the reaction of amineswith metal halides, in particular BiBr₃, already prepared separately.This process is applicable on a laboratory scale, but not at anindustrial level. Metal halides are, in fact, very unstable compounds,dangerous to handle, and as such subject to strict securityrestrictions. The handling of such compounds at an industrial levelwould require complex processing steps, not economically sustainable.

The U.S. Pat. No. 4,935,459 teaches in particular to produce flameretardant compositions made from halogenated compounds of bismuth and/orantimony complexed with melamine. Similarly to the provisions of U.S.Pat. No. 4,798,857 and therefore with the same operating limits, suchcomplexes are produced using metal halides (in particular BiBr₃),prepared separately, as reagents.

A production process which uses separately prepared metal halides asreagents is also described in the scientific publication Costa et al.“Thermal Degradation and Fire Retardancy of Antimony and BismuthTrihalides-Melamine Complexes”, Polymer Degradation and Stability,34(1991) 55-73 and in the scientific publication Bertelli et al. “FireRetardant Systems Based on Melamine Hydrobromide: part I—Fire RetardantBehaviour”, Polymer Degradation and Stability, 18(1987) 225-236.

The effectiveness of organic complexes of halogenated compounds ofbismuth/antimony with amines as flame retardants has therefore beenwell-known for some time. The processes of synthesis are howeverapplicable only in the laboratory on a small scale, and rarelyindustrially feasible given the volatile and dangerous nature of thereagents and of the products obtained.

The difficulties related to a large-scale production have in fact up tonow made widespread use of such compounds impractical.

One industrial application of such compounds is described in the U.S.Pat. No. 5,166,235. The paper describes a masterbatch polypropylenematrix containing halogenated compounds of bismuth/antimony complexedwith amines. The complexes are obtained in situ by reacting melamine andnon-halogenated compounds of bismuth and/or antimony (in particular(BiO)₂CO₃ or SB₂O₃) with hydrohalogen acids (in particular HBr) in thepolypropylene matrix. The process in particular makes it possible toprevent the separate production of metal halides. The process describedin U.S. Pat. No. 5,166,235 has however the significant limitation ofrequiring control of the strength of the reactions, for example byworking at reduced pressure. Such control is essential to prevent thedegradation of the active substances and of the polymeric matrix.

The masterbatch described in U.S. Pat. No. 5,166,235 may only be used onpolypropylene. This represents a significant limitation to theapplicability of the above complexes. The masterbatch is moreoverpresented in the form of spherical-porous particles with relatively lowload limits of the active principle (10-30%). There is therefore a“dilution effect” of the active principle by the polymer matrix which,while on the one hand partially obviating some of the aforementionedtechnical problems, on the other requires much higher quantities ofadditives during use to achieve flame retardancy. By operating this way,the disadvantage for the end user is that of having to take into accountan unwanted polymer matrix which will influence the physical andrheological properties of the product. The polymer masterbatch ismoreover partially irregular inasmuch as synthesised in the cavities ofthe porous polypropylene. Such cavities act as several independentreactors, originating differentiations in composition and the presenceof small agglomerates difficult to disperse subsequently.

PRESENTATION OF THE INVENTION

Consequently, the purpose of the present invention is to eliminateentirely or in part the drawbacks of the prior art mentioned above, bymaking available a preparation process of a flame retardant compositionmade from brominated bismuth and/or antimony compounds complexed withmelamine which is industrially applicable in a simpler way than thecurrently known processes.

A further purpose of the present invention is to provide a preparationprocess of a flame retardant composition made from brominated bismuthand/or antimony compounds complexed with melamine, which is easilycontrollable to avoid degradation of the active compounds.

A further purpose of the present invention is to provide a preparationprocess of a flame retardant composition made from brominated bismuthand/or antimony compounds complexed with melamine, which makes itpossible to easily control the aggressiveness of the reagents, of theintermediates and of the reaction products.

A further purpose of the present invention is to provide a preparationprocess of a flame retardant composition made from brominated bismuthand/or antimony compounds complexed with melamine which makes itpossible to obtain such composition in a pure form, free of polymermatrices, and thus utilisable as a general purpose active principle.

A further purpose of the present invention is to provide a preparationprocess of a flame retardant composition made from brominated bismuthand/or antimony compounds complexed with melamine, which makes itpossible to obtain such composition with properties of chemicalstability and limited aggressiveness.

A further purpose of the present invention is to provide a flameretardant composition made from brominated bismuth and/or antimonycompounds complexed with melamine in a pure form, free of polymermatrices, and thus utilisable as a general purpose active principle.

A further purpose of the present invention is to provide a flameretardant composition made from brominated bismuth and/or antimonycompounds complexed with melamine, which has properties of chemicalstability and limited aggressiveness.

The technical characteristics of the invention according to theaforesaid purposes can be seen clearly from the contents of thefollowing claims and the advantages thereof will be more clearlycomprehensible from the detailed description below,

DETAILED DESCRIPTION

The present invention relates to a preparation process of a flameretardant composition made from brominated bismuth and/or antimonycompounds complexed with melamine and the composition obtained by suchprocess.

As will be clear from the following description, the flame retardantcomposition obtained using the process according to the invention ismade from a mixture of a brominated compound of bismuth and/or antimonycomplexed with melamine and melamine bromohydrate.

According to a general embodiment, the preparation process according tothe invention follows at least one of the two following reactionschemes:Bi₂CO₅+6HBr→2BiBr₃+3H₂O+CO₂BiBr₃+ML→complex ML/BiBr₃HBr+ML→MHB  (I)orSb₂O₃+6HBr→2SbBr₃+3H₂OSbBr₃+ML→complex ML/SbBr₃HBr+ML→MHB  (II)where ML indicates melamine and MHB indicates melamine bromohydrate.

The two reaction schemes essentially differ only in the type of saltused as an initial reagent for the supply of the metal, i.e. bismuthcarbonate (Bi₂CO₅) or antimony sesquioxide (Sb₂O₃). The other reagentsare the same, i.e. melamine and hydrobromic acid.

Preferably the preparation process follows only one of the above tworeaction schemes, introducing into the reaction only one between thebismuth carbonate (Bi₂CO₅) or the antimony sesquioxide (Sb₂O₃). However,it is possible to implement the process by introducing into the reactionboth bismuth carbonate (Bi₂CO₅) and antimony sesquioxide (Sb₂O₃), thusfollowing both the reaction schemes.

Both reaction schemes comprise two main reactions.

A first reaction relates to the synthesis of the ML/BiBr₃ complex anddivides in turn into two reactions that lead in sequence to theformation of an intermediate consisting of the metal bromide through theattack of the metal salt by the acid (as well as the formation ofby-products—only water or water and CO₂—which are then removed from thereaction environment), and then the combination of said intermediatewith melamine to form the complex.

The second reaction, which takes place simultaneously with the first,relates to the synthesis of melamine bromohydrate, through the attack ofthe melamine by the acid.

The formation of the intermediate BiBr₃ is vigorous and exothermic anddevelops a strongly acid environment. In addition, the careless handlingof Br₂ and HBr in the presence of bismuth or antimony or their inorganicsalts may even generate uncontrolled reactions of combustion orexplosion. In addition, the intermediates and reaction productsinvolved, in particular the bromides of the metals and the complexes ofsuch brominated compounds are characterised by high aggressiveness andinstability.

The formation process according to the invention has made it possible tosolve simply and effectively both the problem of controlling theexothermy and the problem of managing the characteristics of theintermediates and final products, making production at industrial levelof such products possible and safe.

In particular, contrary to what is provided for by U.S. Pat. No.5,166,235, the process can be conducted at atmospheric pressure and notat reduced pressure, with benefits in terms of simplification of theplant and control.

Such preparation process comprises the following general operatingsteps:

a) providing the reagents provided for according to one of said tworeaction schemes: melamine; at least one between bismuth carbonate andantimony sesquioxide; and hydrobromic acid in an aqueous solution;

b) placing the above reagents in contact with each other in a reactor soas to trigger said chemical reactions and obtain a complex of brominatedbismuth or brominated antimony with melamine and melamine bromohydrate.

As reactor, in particular, a blade mixer with heating/cooling jacket maybe used.

In particular, the aqueous solution of hydrobromic acid has aconcentration in weight of hydrobromic acid between 40% and 60%.

According to the invention the process comprises a step c) of providingat least one reaction carrier defined by at least one compound selectedfrom the group consisting of melamine, melamine phosphate, melaminepolyphosphate, ammonium phosphate, ammonium polyphosphate, graphite,silica, lignin, triphenyl-phosphate, coke and compounds containingtriazine rings condensed or linked by —NH groups.

Preferably, as compounds containing triazine rings condensed or linkedby —NH groups known compounds such as melam (2,2′-iminobis[4,6-diamine-1,3,5-triazine]; C₆H₉N₁₁ CAS: 3576-88-3), melem(1,3,4,6,7,9,9′-heptaazaphenalene-2,5,8-triamine; C₆H₆N₁₀ CAS:1502-47-2) and melon (CAS: 32518-77-7) are used.

According to an essential aspect of the invention the reagents providedin step a) are placed in contact in step b) in the presence of at leastone compound provided in step c) which acts as a reaction carrier.

The reaction carrier is not involved in said reactions, and remainsalmost chemically and physically unchanged.

As will be clarified in the rest of the description, the presence ofsuch a reaction carrier is essential because it allows the reactions toproceed smoothly and uniformly towards their completion, resolving theproblems noted in the prior art.

The identification of said one or more reaction carriers has made itpossible to industrialise the preparation process of brominatedcompounds of bismuth and/or antimony complexed with melamine, supportingreactions which would otherwise be unmanageable on a large scale.

The use of the reaction carriers defined by the present invention hasalso made it possible to obtain such complexes in the form offormulations that make them easily utilisable, since they do not haveresidual corrosivity, are chemically stable and do not present problemsof photosensitivity.

The flame retardant compositions obtained with the process according tothe invention show enhanced flame retardancy properties compared tosimilar compositions made from the aforesaid complexes. This isattributable to the combined presence of the ML/MeBR₃ complex and themelamine bromohydrate in the final composition.

Advantageously, the step b) in which the reagents are placed in contactwith each other may take place in the presence of only one reactioncarrier, preferably melamine, or of two or more different reactioncarriers.

In the case in which melamine is used as a reaction carrier, alone or incombination with other compounds, the total quantity of melamineintroduced into the reactor is in excess of the stoichiometric amountrequired in relation to the quantities of the other reagents. In otherwords, the melamine will be introduced in such quantity as to itself(alone or together with the further reaction carrier) constitute asupport as well as the main reagent for the formation of the flameretardant complex. At the end of the reactions, part of the melamineintroduced will in turn be brominated, while the amountstoichiometrically in excess will remain almost unchanged chemically andphysically.

The reaction carrier may thus be: melamine alone, in excess of thestoichiometry indicated in the aforementioned reactions; or mixtures ofmelamine with melamine phosphate, melamine polyphosphate, ammoniumpolyphosphate, graphite, silica, lignin, triphenyl phosphate, coke andcompounds containing triazine rings condensed or linked by —NH groups(melam, melem, melon for example); or one or more of the compoundsselected from melamine phosphate, melamine polyphosphate, ammoniumpolyphosphate, graphite, silica, lignin, triphenyl phosphate, coke andcompounds containing triazine rings condensed or linked by —NH groups(melam, melem, melon for example), without melamine in excess.

According to the invention, said reagents (melamine; at least onebetween bismuth carbonate and antimony sesquioxide; and hydrobromic acidin aqueous solution) are introduced into the reactor in an amountdefined by the stoichiometric ratios according to one of the aforesaidtwo reaction schemes.

As already mentioned above, the formation of the complex (ML/BiBr₃and/or ML/SbBr₃) is independent of the formation of melaminebromohydrate. This makes it possible to modulate the final content ofcomplex and of melamine bromohydrate in the final composition, varyingthe initial amount of the metal salt and of the melamine. Thestoichiometric ratios therefore relate to the amount of the metal saltin relation to the hydrobromic acid and to the melamine for theformation of the complex, and to the amount of melamine in relation tothe hydrobromic acid for the formation of the melamine bromohydrate.

The bromination of part of the melamine makes it possible to have thesimultaneous presence of “two types” of bromine with differentstoichiometries and effects in terms of flame retardant action.Depending on the type of polymer or, more generally, the type ofapplication the flame retardant composition according to the inventionis intended for, it is possible to vary the ratio between the two typesof bromine.

According to the invention, the reaction carrier is introduced into thereactor in an amount defined with respect to the total weight of thereagents so that it can perform a modulator function.

Since the reaction carrier acts as a “modulator” of the vigour of thereactions, but is not involved in any of these, it is not tied to theseby any stoichiometry. The reaction carrier need only be present inweight in minimum quantities such as to be able to perform its“modulator” function.

“Reaction modulator” is understood to mean one or more compounds whichin terms of physical and chemical characteristics (i.e. stability inreaction conditions, chemical compatibility, etc. . . . ) and/or due totheir ponderal presence remain inert during the synthesis of thebrominated components creating however the conditions (temperature, pH,level of chemical inertia, etc. . . . ) such as to make such reactions,per se excessively vigorous, realisable simply and safely at theindustrial level.

The amount in weight of the reaction carrier may vary depending on thetype of compound or compounds selected.

Preferably, the reaction carrier (whether defined by a single compoundor two or more compounds) is introduced in an amount of not less than 8%in weight with respect to the total weight of the reagents. As describedfurther below, in the final product—following the removal of somereaction by-products such as water or CO₂—said minimum weight of thereaction carrier is raised to 10% in weight.

According to the invention, polymeric compounds are not introduced inthe reactor, at least not in such quantities as to create a polymermatrix. Small amounts of polymers may possibly be present, but not insuch quantities as to form a polymer matrix such as to limit the use ofthe flame retardant composition to specific polymers. In particular, anypolymers may be present in amounts not exceeding 3% in weight of thetotal weight of the flame retardant composition. In particular,polymeric resins may be present as compatibilizing agents, protectiveagents and more generally as “improvement additives” of theapplicability of the flame retardant composition of the invention.

This way, as will be clarified in the rest of the description, the flameretardant composition according to the invention is utilisable as ageneral purpose active principle.

Preferably, the reagents are placed in contact with each other in thepresence of the reaction carrier under continuous stirring.

The reagents and reaction carrier can be introduced into the reactorsimultaneously. However, a mode with temporally differentiatedintroduction of the reagents is preferred to this—theoreticallypossible—operating mode.

Preferably, the contact between the reagents in the presence of thereaction carrier takes place in two distinct sub-steps:

-   -   b1) introducing into the reactor the melamine, the reaction        carrier and at least one between the bismuth carbonate and        antimony sesquioxide under continuous stirring to form a        mixture; and    -   b2) adding to the aforesaid mixture under continuous stirring        the hydrobromic acid in aqueous solution so as to trigger the        aforementioned chemical reactions.

Regardless of the mode and sequence of introduction of the reagents inthe reactor, the preparation process of the flame retardant compositionmade from brominated compounds of bismuth and/or antimony complexed withmelamine is a “one step” process in the sense that the separatepreparation of the brominated compounds of bismuth or antimony is notprovided for, but all the reactions take place in the same reactionenvironment. This makes the process industrially easier to manage.

The process according to the invention can also be defined as a processthat takes place in situ, in the sense that none of the reactionproducts, in particular the more unstable or potentially dangerous, isprepared or handled out of the reactor.

Advantageously, as will be described in more detail below, thepreparation process according to the invention may be conducted througha dry or semi-dry pathway or through a wet pathway. The choice betweenthe two pathways is carried out mainly by acting on the introductionmode of the bromide acid in the reactor, as well as on the initialphysical state of the reagents.

The dry or semi-dry pathway is chosen in the case of wishing to maintainthroughout the reaction a physical form of the raw reaction product thatcan be processed in a mixer for powders (thus in the form of a paste orsemi-dry at each step). In this case, the modulation of the rate ofaddition of the acid is a key point in the management of the economy ofthe process.

The wet pathway process is chosen, instead, in the case in which thereis a need or interest in having a liquid raw reaction product, so as toachieve a greater product homogeneity. As will be clarified below, thewet pathway process combined with a spray-drying technique makes itpossible to obtain dry products in the form of powders with particularparticle sizes without the need for further processing of the finalproduct, such as micronisation. In this case, the modulation of the rateof addition of the acid is not a key point in the management of theeconomy of the process. Compared to the dry pathway it is possible todose the acid faster or, possibly even introduce it into the reactionenvironment all together.

According to a first particular embodiment of the process according tothe invention, relative to the dry or semi-dry pathway, the melamine,the reaction carrier and at least one between the bismuth carbonate andantimony sesquioxide are introduced into the reactor in the dry state,preferably in the form of powders.

Preferably, inside the reactor the melamine, the reaction carrier and atleast one between the bismuth carbonate and antimony sesquioxide aresubjected to continuous stirring.

Advantageously, before the addition of the hydrobromic acid, the mixtureof melamine, the reaction carrier and at least one between the bismuthcarbonate and antimony sesquioxide is preheated. Preferably, the powdersare preheated to a temperature between 60° C. and 90° C. It has beenfound experimentally that this range of temperatures, even consideringthe residual exothermy of the reaction, permits an optimal evaporationof the water once the hydrobromic acid has reacted. This temperaturerange also represents a good compromise between production costs (toheat the reactor) and the requirements of said process.

Thanks to the preheating of the powders, the evaporation of water rightfrom the earliest stages of dosing the aqueous solution of hydrobromicacid is favoured, and the reaction mass is thus maintained in a semi-dryor mixable paste state.

Preferably, the hydrobromic acid in aqueous solution is added to themixture of melamine, reaction carrier and at least one between thebismuth carbonate and antimony sesquioxide following a controlleddosage, in order to keep the mass of reagents and reaction productsalways in a semi-dry form or in the form of a workable paste. Thecontrolled dosage of the aqueous solution of hydrobromic acid preventsan abrupt increase in the water content in the mass of reagents. Thanksto the phenomenon of evaporation of the water induced by the exothermyof the reactions, it is thus possible to limit the water content in themass of reagents and reaction products.

Preferably, the controlled dosage of the acid is anticipated by apreheating of the powders. As already anticipated, the preheating of thepowder helps to promote the evaporation of water gradually as theaqueous solution of acid is added and water is formed as a reactionproduct.

In particular, the hydrobromic acid in aqueous solution (preferably40%-60% in weight of hydrobromic acid) is dosed in the dry state mixturewith a ponderal dosing rate of between 8 and 11%/h of the total weightof the reagents and reaction carrier.

Advantageously, the mass of reagents and reaction carrier is kept undercontinuous stirring during and after the dosing of the acid.

The pathway of formation of the reaction products and their maintenancein a more or less fine solid form is thus guided by the regularity andrate of addition of the aqueous solution of the hydracid, and by theheating of the mass kept in movement by the action of the kneadingblades. This way, the water of the hydracid and that of the reactionwill be removed from the mixture gradually as it is added and/or formed,thus ensuring stoichiometry and uniformity of result.

Advantageously, after having added the whole amount of hydrobromic acid,the reactor is heated to remove all the water present and fully dry thereaction products, thus obtaining a dry raw product. In particular, thereactor is heated to a temperature between 100° C. and 140° C. Suchtemperatures are sufficient to ensure the desired drying in“industrially reasonable” times (e.g. in the case of a batch of 1000 kgthe raw product is dried in about 2 hours). The temperature may beincreased up to about 240° C. to reduce the drying times, withoutdamaging the reaction product. Heating to 240° C. is not preferred,however, given the high costs needed to bring a large mass to a highertemperature.

This way at the end of the reaction a 100% pure powder is obtained whichhas not to undergo industrially complex treatment such as, for example,filtration, recovery of the active principle from the liquid,distillation, etc . . . .

Advantageously, the dry raw product obtained at the end of heating issubjected to a micronisation process, aimed at obtaining powders withthe desired particle size.

Preferably this micronisation process is conducted to bring theparticles of the solid raw product to have a uniform mean particle size.Preferably the mean particle size is between 5 μm-50 μm, more preferablybetween 20 μm-30 μm or between 5 μm-10 μm.

Advantageously, following the dry or semi-dry pathway specific additivescan be introduced before, during or after the dosing of the hydrobromicacid in the reactor.

In particular, compatibilising/water-repellent agents and/or agentsfacilitating the handling of the finished product in the applicationphase thereof to the intended matrix may be introduced, preferably atthe end of the reactions, i.e. at the end of the dosing of the acid.

In particular, after the complete drying of the reaction products andprior to the micronisation process, at least one water repellent agentor compatibilizer, consisting in particular of one or more compoundshaving a softening point between 60° C. and 100° C., such as paraffin orpolyester waxes preferably stearic acid, may be added to the dry rawproduct.

Advantageously, after the complete drying of the reaction products andbefore the micronisation process, at least one agent capable offavouring the handling of the finished product in the application phaseof the latter to the intended matrix, such as silica, may be introducedinto the reactor.

According to a second particular embodiment of the process according tothe invention, relative to the wet pathway, the melamine, the reactioncarrier and at least one between the bismuth carbonate and antimonysesquioxide are introduced into the reactor preferably in the form ofpowders, together with the water, obtaining a suspension.

Preferably, inside the reactor the melamine, the reaction carrier, atleast one between the bismuth carbonate and antimony sesquioxide and thewater are subjected to continuous stirring.

Advantageously, unlike the dry or semi-dry pathway, it is not necessaryto preheat the melamine, metal salt and reaction carrier in the aqueoussuspension.

The water is present in an amount such as to ensure that after theaddition of the hydrobromic acid, the reactions take place in solution.

Preferably, the hydrobromic acid in aqueous solution is added to theaforesaid suspension in water of melamine, of the reaction carrier, andof at least one between the bismuth carbonate and antimony sesquioxidewithout heating the reactor.

In the case of the wet pathway, the modulation of the rate of additionof the acid is not a key point in the management of the economy of theprocess. Compared to the dry pathway it is possible to dose the acidfaster or, possibly even introduce it into the reaction environment alltogether.

Preferably, the hydrobromic acid in aqueous solution is added to theaforesaid suspension adopting a controlled dosage which is functional tooptimal management of the process, in particular in terms of handlingthe reagent (for example by means of pumps), of observance of safetyprocedures and of control of the chemical reactions.

Advantageously, the mass of reagents and reaction carrier is maintainedin continuous stirring during and after the dosing of the acid.

After adding the whole amount of hydrobromic acid, a raw reactionproduct in aqueous suspension is obtained.

Preferably, after adding the whole amount of hydrobromic acid, the rawreaction product in aqueous suspension is subjected to drying to obtaina dry raw product.

The drying of the aqueous suspension may be carried out using anytechnique suitable for the purpose, such as vacuum drying or drying inrotating cylinders, by means of suitably chosen ovens, evaporators, etc.The drying step is then followed by a micronisation step aimed atbringing the particles of the dried raw product to have a uniform meanparticle size. Preferably, the mean particle size is between 5 μm-50 μm,more preferably between 20 μm-30 μm or between 5 μm-10 μm.

Preferably, the drying is achieved by pulverisation drying or a spraydrying technique, which makes it possible to dry the aqueous suspensionto obtain a dry product with a uniform particle size without amicronisation step. The spray-drying technique, in fact, permits veryflexible control of the properties of the particles of powder such asparticle size, density, moisture content, etc. . . . ; for this reason,if properly applied, it makes it possible to avoid steps which couldprove industrially costly such as the crushing and micronisation of thefinished product.

Substantially, the “spray drying” technique (in itself known to a personskilled in the art) is based on the possibility of producing powders ofa controlled particle size and shape directly from an aqueous suspensionby evaporation of the solvent. The process is based on mixing a heatedgas (usually steam) with an atomized liquid, thus physically composed ofdroplets with a high surface/mass ratio (thus maximising the heatexchange) inside a container (drying chamber) and determining, by directcontact, the rapid and uniform evaporation of the solvent present in theliquid.

The process of pulverisation or spray drying comprises three stages:atomization of the liquid to be dried; drying; and separation of thepowder obtained from the wet gas. This type of technique determines aconsiderable thermal shock to the products to be dried. The flameretardant composition of the present invention, as will be describedbelow, however, has shown thermal and chemical characteristics such asto advantageously allow the use of such drying technique in the laststep of the wet pathway process.

Advantageously, thanks to the excellent thermal properties of the flameretardant composition according to the invention, the aqueous suspensioncan be dried using a spray drying technique known as “gatedrier”. The“gatedrier” (in itself known to a person skilled in the art) is a spraydryer improved in size and performance. The peculiarity of the gatedrieris its ability to work with input temperatures of the hot air even 50°C. higher than in normal spray drying techniques (for reasons of savingsin time and energy).

Advantageously, the water content of the aqueous suspension can beregulated depending on the conditions of viscosity required by thedrying treatment, in particular in the case of pulverization or spraydrying.

Advantageously, after the drying process, the raw dry product may betreated with at least one water repellent agent and/or compatibilizer,preferably having a softening point between 60° C. and 100° C. such asparaffin waxes, preferably stearic acid. Advantageously, after thedrying process, the raw dry product may be treated with at least oneagent, such as silica, capable of favouring the handling of the finishedproduct in the application phase thereof to the matrix for which it isintended.

Some examples of preparation of a flame retardant composition accordingto the process of the present invention are given below.

The bromine content of the flame retardant composition was determined byacid-base titration, dispersing 0.5 g of the composition in 100 ml ofwater, under magnetic stirring, heating to 50° C. and then adding a fewdrops of phenolphthalein. The suspension thus obtained was titrated witha 0.1 N solution of NaOH.

Example 1 (Dry or Semi-Dry Synthesis)

500 kg of melamine C₃H₆N₆ and 100 kg of bismuth basic carbonate(Bi₀)₂CO₃ were introduced under agitation into a “four wire coils” mixerwith jacket, with a capacity of about 1500 liters, fitted with a heatingand cooling system. Heating of the oil in the jacket is performed untilthe powders reach a temperature of 75-80° C. Once reached thistemperature, 434 kg of aqueous solution of hydrobromic acid 48% HBr weredosed by means of a membrane pump at the rate of about 90 kg/h (whichcorresponds to about 10% w/w/h). During the dosing of the acid (i.e. inconjunction with the development of the reactions), the raw reactionproduct remains at all times in the semi-dry state and the temperaturerises to settle around 100-105° C. (optimum temperature for theevaporation of the secondary product: water).

After dosing the acid the reactor is heated up to bring the “vapours” toabout 120° C. and thus achieve the removal of all the water stillpresent in the reaction environment and the complete drying of the rawproduct. The pH of the water coming from the condenser of the reactor ismeasured. This pH remains substantially neutral throughout the entirereaction, proving that all the fed hydrobromic acid enters into thereaction and that the by-products leaving the reactor do not retainsignificant residual acidity.

Still at the temperature of 120° C., 8 kg (about 1% in weight of thetotal) of stearic acid is then added to give water-repellence to thefinished product, the heating is interrupted and the product is left tocool spontaneously under agitation inside the reactor. At this point, tomake the powder in question more “fluid” 1.6 kg of silica (about 0.2% inweight of the total) is added and left to mix for a further 30 min. Theproduct is then micronised with d₉₅<30 microns. The product thusobtained has a bromine content of about 26%, a pH in aqueous suspensionof about 5.7 and a thermal resistance above 230° C. (loss≤2% after 15min of permanence in a muffle furnace with air circulation at thistemperature).

850 kg of finished product are obtained having the following compositionin weight: 36.5% melamine bromohydrate; 28.5% melamine/BiBr₃ complex;35% melamine; total bromine=26%.

Example 2 (Wet Synthesis)

In a pilot mixer (paste and liquid-tight) with a capacity of about 150liters and fitted with a heating/cooling jacket, the following areintroduced with vigorous stirring: 25 kg of melamine, 5 kg of bismuthbasic carbonate and 61 kg of water. To this suspension, kept inagitation and making cooling oil circulate in the jacket, 21.7 kg ofaqueous solution of 48% HBr are added. During the dosing of the acid thetemperature never exceeds 70° C. The resulting suspension (pH=5.5) isthen sprayed in a “gate” drier at a pressure of 16 MPa and an outputtemperature of 95° C.

40 kg of finished product are obtained in powder form, which maypossibly be treated with stearic acid for water-repellence and toincrease compatibility with the polyolefins and treated with silica toincrease its fluidity in handling, with the following composition inweight: 36.5% melamine bromohydrate; 28.5% melamine/BiBr₃ complex; 35%melamine; total bromine=26%.

Example 3

In a pilot mixer with a capacity of about 150 liters, 50 kg of melamineand 10 kg of bismuth sub-carbonate kept under vigorous agitation areheated to 75-80° C. As in Example 1, the acid aqueous solution is dosedat a rate of 10% w/w/h, this time in the amount of 67.7 kg, so as tokeep the raw reaction product always in the semi-dry state. The pH ofthe “recondensed” water is checked and kept neutral in all the steps.The temperature inside the reactor is kept below 105° C. throughout thedosing of the acid.

90 kg of product are obtained with the following composition in weight:64.3% melamine bromohydrate; 24.7% melamine/BiBr₃ complex; 11% melamine;total bromine=35%; pH in aqueous suspension=5.2.

Compared to Example 1, the ratios of the reagents have been modified toincrease the bromine content of the MHB component.

Example 4

With the same procedures and equipment as Example 3, 40 kg of melamineare reacted with 25 kg of bismuth carbonate and 65 kg of aqueoussolution of 48% HBr. The raw reaction product remains in the semi-drystate at all times and the water in output from the condenser has aneutral pH during all steps of the process. The maximum temperaturereached during the reaction remains below 105° C.

90 kg of finished product are obtained having the composition: 20.5%melamine bromohydrate; 61.8% melamine/BiBr₃ complex; 17.7% melamine;total bromine=34%; pH in aqueous suspension=5.

Compared to Example 1, the ratios of the reagents have been modified toincrease the bromine content of the ML/BiBr3 complex component.

Example 5 (Use of Sb)

With the same procedures and equipment as Example 3, 50 kg of melamineare reacted with 6.25 kg of antimony sesquioxide and 43.2 kg of 48%aqueous solution of HBr. The raw reaction product remains in thesemi-dry state at all times and the water in output from the condenserhas a neutral pH during all steps of the process. The maximumtemperature reached during the reaction remains below 105° C.

113 kg of product are obtained with the following composition in weight:35.2% melamine bromohydrate; 29.8% melamine/BiBr3 complex; 35% melamine;total bromine=27%; pH in aqueous suspension=5.4.

Example 6 (Use of Reaction Carriers Other than Melamine)

With the same ways and equipment as example 3, 5 tests are conductedusing as a “reaction carrier” the compounds and amounts as specifiedbelow:

a) 23 kg of melamine, 27 kg of Melamine phosphate, 10 kg of bismuthsubcarbonate and 43.4 kg of an aqueous solution of 48% HBr. 80 kg offinished product are obtained with a composition in weight: 36.3%melamine bromohydrate; 28.4% melamine/BiBr₃ complex; 35.3% melaminephosphate; total bromine=26.1%.

b) 23 kg of melamine, 27 kg of Melamine polyphosphate, 10 kg of bismuthsubcarbonate and 43.4 kg of an aqueous solution of 48% HBr. 80 kg offinished product are obtained having the composition: 36.3% melaminebromohydrate; 28.4% melamine/BiBr₃ complex; 35.3% melaminepolyphosphate; total bromine=26%.

c) 23 kg of melamine, 27 kg of ammonium polyphosphate, 10 kg of bismuthsubcarbonate and 43.4 kg of an aqueous solution of 48% HBr. 80 kg offinished product are obtained with a composition in weight: 36.3%melamine bromohydrate; 28.4% melamine/BiBr₃ complex; 35.3% ammoniumpolyphosphate; total bromine=26.2%.

d) 23 kg of melamine, 27 kg of graphite, 10 kg of bismuth subcarbonateand 43.4 kg of an aqueous solution of 48% HBr. 80 kg of finished productare obtained with a composition in weight: 36.3% melamine bromohydrate;28.4% melamine/BiBr₃ complex; 35.3% graphite; total bromine=26.2%.

e) 36.5 kg of melamine, 13.5 kg of silica, 10 kg of bismuthsub-carbonate and 43.4 kg of an aqueous solution of 48% HBr. 80 kg offinished product are obtained having the composition: 36.3% melaminebromohydrate; 28.4% melamine/BiBr₃ complex; 17.5% silica; 17.8%melamine; total bromine=25.8%.

The reaction temperature observed during the performance of the batchesindicated in example 6 is kept in each case below 105° C. and the pH ofthe individual finished products reported is confirmed in each case asbetween 5 and 6.

All examples 1 to 6 reported above were conducted at atmosphericpressure.

The monitoring of the pH of the water in output from the reactor and ofthe suspension containing the finished product confirms the fact thatthe products and by-products of the reaction obtained using the processaccording to the invention have residual mild acidity (pH not lower than5). From the experimental data it can be seen that at the end of thereactions in the reactor there is a very low level of acidity, due tothe fact that the acid has completely reacted. Lastly, it may beconcluded that in working conditions, the reaction product presentssubstantially no acidity. This evidence can be expressed in other termssuch as “limited aggressiveness” which will presumably have a verypositive impact on the “average life” of the plants of production andsubsequently on the plants of processing/application of the brominatedcomplexes thus obtained.

The present invention also relates to a flame retardant composition madefrom brominated bismuth and/or antimony compounds complexed withmelamine.

Preferably, but not necessarily such a composition is obtained using theprocess according to the present invention.

According to the invention, the flame retardant composition, is composedof:

-   -   a complex having a formula ML (MeBr3), where ML indicates        melamine and Me is bismuth or antimony;    -   melamine bromohydrate;    -   at least one among the compounds chosen from the group        consisting of melamine, melamine phosphate, melamine        polyphosphate, ammonium phosphate, ammonium polyphosphate,        graphite, silica, lignin, triphenyl-phosphate, coke and        compounds containing triazine rings condensed or linked by —NH        groups; and    -   possible additives.

Preferably, as compounds containing triazine rings condensed or linkedby —NH groups known compounds such as melam (2,2′-iminobis[4,6-diamine-1,3,5-triazine]; C₆H₉N₁₁ CAS: 3576-88-3), melem(1,3,4,6,7,9,9′-heptaazaphenalene-2,5,8-triamine; C₆H₆N₁₀ CAS:1502-47-2) and melon (CAS: 32518-77-7) are used.

Preferably, the composition is in the form of dry powder, with meanparticle size between 5 μm-50 μm. Preferably the particle size isbetween 20 μm-30 μm or between 5 μm-10 μm.

Advantageously the flame retardant composition does not comprisepolymeric compounds, at least not in such quantities as to create apolymer matrix. Small amounts of polymers may possibly be present, butnot in such quantities as to form a polymer matrix such as to limit theuse of the flame retardant composition to specific polymers. Inparticular, any polymers may be present in amounts not exceeding 3% inweight of the total weight of the flame retardant composition. Inparticular, polymeric resins may be present as compatibilizing,protective agents and more generally as “improvement additives” of theapplication of the flame retardant composition of the invention.

As will be explained in the rest of the description, with reference toexperimental tests conducted, the flame retardant composition accordingto the invention gives excellent flame-retardant properties to thepolymers it is dosed in. Such properties emerge even at low dosages.

The flame retardant composition according to the invention has noresidual aggressiveness, is chemically stable and does not present theproblems of photosensitivity emerging for example in the scientificpublication Costa et al. “Thermal Degradation and Fire Retardancy ofAntimony and Bismuth Trihalides-Melamine Complexes”, Polymer Degradationand Stability, 34(1991) 55-73. Moreover, the flame retardant compositionaccording to the invention has a considerable versatility of useresulting from the possibility of varying the “type and content” ofbromine present depending on the needs and specific affinities of thesingle component (complex or melamine bromohydrate) with the chosenmatrix (polymer type, resin type, etc. . . . ).

According to a general embodiment of the invention, the flame retardantcomposition is composed of:

-   -   20-65% in weight of the aforesaid complex ML (MeBr3);    -   20-65% in weight of melamine bromohydrate;    -   10-40% in weight of at least one among the compounds chosen from        the group consisting of melamine, melamine phosphate, melamine        polyphosphate, ammonium phosphate, ammonium polyphosphate,        graphite, silica, lignin, triphenyl-phosphate, coke and        compounds containing triazine rings condensed or linked by —NH        groups;    -   0-3% of additives.

According to a first particular embodiment, the flame retardantcomposition is composed of:

-   -   25-35% in weight of the aforesaid complex ML (MeBr3);    -   25-35% in weight of melamine bromohydrate;    -   25-30% in weight of at least one among the compounds chosen from        the group consisting of melamine, melamine phosphate, melamine        polyphosphate, ammonium phosphate, ammonium polyphosphate,        graphite, silica, lignin, triphenyl-phosphate, coke and        compounds containing triazine rings condensed or linked by —NH        groups;    -   0-3% of additives.

This first embodiment is particularly suitable to be used inapplications in which, in addition to the fire retardant (FR) actionperformed by the two types of bromine present roughly in the samequantities, the presence of a significant amount of reaction carrier(about one third) acquires a central role. “Central role” may, forexample, be understood as a modulation of the residual chemicalaggressiveness of the additive on the operators, in particular in thecase in which the reaction carrier comprises melamine, silica, lignin,etc. . . . ; or an FR-synergic action supplied, for example, in the casein which the reaction carrier comprises phosphates; or even an effect onthe total thermal conductivity in the case in which the reaction carriercomprises graphite or coke, and so forth.

According to a second particular embodiment, the flame retardantcomposition is composed of:

-   -   55-65% in weight of said complex having the formula ML (MeBr3);    -   20-25% in weight of melamine bromohydrate;    -   10-20% in weight of at least one among the compounds chosen from        the group consisting of melamine, melamine phosphate, melamine        polyphosphate, ammonium phosphate, ammonium polyphosphate,        graphite, silica, lignin, triphenyl-phosphate, coke and        compounds containing triazine rings condensed or linked by —NH        groups;    -   0-3% of additives.

This second embodiment is particularly suitable to be used when thematrix (polymeric or otherwise) in which the flame retardant compositionis incorporated, in addition to requiring a given intake of totalbromine, is also particularly sensitive to the flame retardant action ofthe complex of formula ML (BiBr3) and chemically similar to it.

According to a third particular embodiment, the flame retardantcomposition is composed of:

-   -   20-25% in weight of said complex having the formula ML (MeBr3);    -   55-65% in weight of melamine bromohydrate;    -   10-20% in weight of at least one among the compounds chosen from        the group consisting of melamine, melamine phosphate, melamine        polyphosphate, ammonium phosphate, ammonium polyphosphate,        graphite, silica, lignin, triphenyl-phosphate, coke and        compounds containing triazine rings condensed or linked by —NH        groups;    -   0-3% of additives.

This third embodiment is particularly suitable to be used when thematrix (polymeric or otherwise) in which it is incorporated, in additionto requiring a given intake of total bromine, is also particularlysensitive to the anti-flame action of the melamine bromohydrate andchemically similar to it.

Preferably, the flame retardant composition is composed of: the complexML (MeBR₃); melamine bromohydrate; melamine; and possible additives.Preferably, the compositions in weight of the various componentscorrespond to those indicated in the embodiments described above.

In particular, the additives may consist ofcompatibilizing/water-repellent agents and/or agents which facilitatethe handling of the composition in question at the application stagethereof to the matrix for which it is intended, such as silica.

In particular, the water-repellent/compatibilizing agents are preferablyone or more compounds having a softening point between 60° C. and 100°C., such as paraffin waxes or a polyester, preferably stearic acid.

As previously indicated, the flame retardant compositions according tothe invention, in particular those obtained using the preparationprocess according to the invention, may exert a strong action as flameretardants in many polymeric materials, such as, polypropylene and itscopolymers, polystyrene (crystal and buffer), nylon 6 and 66, PBT.

To evaluate the effectiveness of the flame retardant compositionsaccording to the invention some tests were conducted on specimens ofpolymers to which such compositions were added.

The polymer mixtures with the flame retardant compositions according tothe invention added to them were obtained by mixing in a Brabendermixer, at a temperature equal to or higher than the softeningtemperature of the polymer they were destined to.

The polymeric mixtures added contain from 1 to 30% in weight of theflame retardant composition according to the invention and from 0 to 1%in weight of a promoter of free radicals, such as2,3-dimethyl-2,3-diphenyl butane or poly 1,4-diisopropyl benzene, orothers of the same type/function.

In general, the radicals promoter is usually introduced into thecompound to stimulate “dripping”, which is one of the mechanisms bymeans of which a flame retardant can carry out its function. Flameretardants which act only by “dripping” do not exert their functionexcept in the presence of a radicals promoter, other retardants insteadwork equally well in the absence of a radicals promoter (using othermechanisms). The flame retardant properties according to the inventionwere verified by investigating behaviour both in the presence andabsence of radicals promoters. Where required and permitted, theradicals promoter also makes it possible to significantly lower theamount used of the flame retardant.

The compounds thus obtained are converted, by moulding, into plates witha thickness of 3.2 mm from which the specimens (123 mm×13 mm) are cutfor measuring flame resistance.

The level of flame resistance was determined by measurements of theIndex of oxygen (in compliance with ASTM 2863) and/or by determining theextinguishing time by application of the standard UL-94 (UnderwriterLaboratories—USA)

The oxygen index (01) represents the minimum concentration of oxygen(expressed in % volume) in an oxygen-nitrogen mixture which allows thesample of the test material, after ignition with a butane gas burner, tocontinue to burn for three minutes and/or for 50 mm of its length: thehigher the value of the oxygen index (01), the greater itsflame-resistance.

The UL-94 test is conducted on samples placed vertically and havingdifferent thicknesses coded by the method. As already mentioned, thetests used only specimens of 3.2 mm thickness, corresponding to theeighth of an inch described in the standard. The burner flame is placedin contact with the lower edge of the sample at an angle of 45°. Fromthe moment it is removed, the time in which the specimen stops burningand whether it lets drops of molten polymer fall during combustion, isrecorded.

Based on its behaviour, the material is thus classified:

V-0: when the extinguishing time of the flame is less than or equal to 5seconds (mean value of 5 samples for 2 consecutive ignitions). Noflaming droplets should fall.

V-1: when the extinguishing time is less than or equal to 25 sec. Noflaming droplets should fall.

V-2: when, although extinguishing itself, the sample lets flamingdroplets fall able to ignite a ball of cotton wool placed 30 cm underit.

Sample Preparation and Characterization of Flame Retardancy (FR)Performance

In order to evaluate their performance as flame retardants, polymericmixtures were prepared containing the flame retardant compositions asobtained from the examples 1-7 according to the process of the inventionalready described. The samples to be subjected to the flame resistancetest are prepared in a Brabender laboratory mixer working at a speed of30 rpm and with a chamber temperature of 180° C. and a temperature ofthe circulating oil kept at 220° C.

The quantity and nature of the various components is been indicated inthe tables below together with the flame resistance results. Inparticular, Tables 1 and 2 report the results of the flame-resistancetests conducted on polymeric formulations containing differentthermoplastic materials and flame retardant composition obtained fromthe application of the process according to the invention as inexample 1. Tables 3 and 4 instead shows the flame resistance data of thepolymeric formulations containing flame retardant compositions preparedaccording to examples 1-6 and the sole polypropylene Moplen HF501N.

The following materials were used:

Moplen® HF501N PP: polypropylene marketed by LyondellBasell;

Dutral CO054: ethylene-propylene copolymer (60% ethylene) marketed byVersalis Spa;

Edistir N1840: crystal polystyrene marketed by Versalis Spa;

Pibiflex 2560: polyester marketed by P-GROUP Spa;

CCPIB: poly-1.4-diisopropylbenzene (radical promoter) marketed byPeroxitalia Ltd;

CCDFB: 2.3 dimethyl-2,3-diphenyl butane (radical promoter) marketed byPeroxitalia Ltd.

TABLE 1 PP moplen 100 95 90 85 70 98.5 60 88 87 HF501N Dutral CO054 — —— — — — 10 10 10 FR (Example1) — 5 10 15 30 1 30 1.5 2 CCPIB — — — — —0.5 — 0.5 1 Oi 18 20.5 21.5 24.5 25.5 32 25.5 25.5 24.5 UL-94 B B V-2V-2 V-2 V-2 V-2 V-2 V-2 Extinguishing times (s) 6; 20; B 1; 1; 10 1; 1;1 1; 1; 1 1; 1; 16 1; 1; 1 1; 1; 1

The data in Table 1 show that by adding only 5% of the flame retardantcomposition to the polymer of Example 1, the resulting compound shows“flame retardant” activity even though it did not pass the UL-94 VBtest; an increase of approximately 2.5 index points of oxygen passingfrom the virgin matrix (col.2) to the compound containing 5% of additive(col. 3) is in fact observed.

All the flame retardant compositions prepared according to the processof the invention were tested in two ways preparing polymeric compounds:alone (without other synergists) in medium-high loaded compound (FRcomposition not less than 15% in weight) or in very low quantities inthe presence of a radicals promoter. Table 1 shows how both solutionsare effective even though the second proves preferable. When a certainproportion of ethylene (with Dutral C0054) is inserted the compound, asmall extra amount of additive is sufficient to obtain good flameretardancy (FR) performance, even though it is known that the presenceof ethylene disturbs the FR activity in this type of application.

TABLE 2 Edistir N1840 100 98.5 — — (comparative) Pibiflex 2560 — — 10098.5 (comparative) FR (example 1) — 1.25 — 1.25 CCDFB — 0.25 — 0.25 Oi 18 22  17 21

Table 2 shows how even a small amount of flame retardant compositionfrom the process presented in example 1 in the presence of a radicalspromoter makes it possible to achieve a good degree of flame resistanceon the various polymer matrices tested.

TABLE 3 FR 15 — — — 1.25 — — — — (example 2) FR — 15 — — — 1.25 — — —(example 3) FR — — 15 — — — 1.25 — — (example 4) FR — — — 15 — — — —1.25 (example 5) CCPIB — — — — 0.25 0.25 0.25 0.25 0.25 Oi 27 24.5 26.523 31.5 26.5 31 24.5 23 UL-94 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 —Extinguishing 1; 1; 1 1; 14; 1 1; 5; 1 1; 18; 10 1; 1; 2 1; 1; 1 1; 1; 11; 1; 1 — times (s)

Tables 3 and 4 show the excellent level of “flame retardant” efficacy ofthe compositions prepared according to the process of the invention(examples 2 to 6)

TABLE 4 FR (example 6a) 15 — — — — 1.25 — — — — FR (example 6b) — 15 — —— — 1.25 — — — FR (example 6c) — — 15 — — — — 1.25 — — FR (example 6c) —— — 15 — — — — 1.25 — FR (example 6e) — — — — 15 — — — — 1.25 CCPIB — —— — — 0.25 0.25 0.25 0.25 0.25 Oi 21 26 21 26 20 29 28 25 32 30.5 UL-94V-2 V-2 V-2 V-2 B V-2 V-2 V-2 V-2 V-2 Extinguishing 1; 3; 6 25; 1; 1 5;1; 1 1; 5; 1 — 1; 1; 1 1; 1; 1 1; 1; 1 1; 1; 1 1; 1; 1 times (s)

TABLE 5 comparison comparison 1 2 PP moplen Complement to 100 net ofstabilisers HF501N FR — 1 — — — 0.6 — — (example 1) FR 1.25 — — — 0.6 —(example 4) FR — — — 1.25 — — — 0.6 (example 6d) ML/BiBr₃ — — — — 0.5 —— — complex Melamine 1.5 — — — — — — — bromohydrate Bismuth 0.2 — — — —— — — subcarbonate CCPIB 0.2 0.5 0.25 0.25 0.3 0.15 0.15 0.15 Oi 31.5 3231 32 29.5 29 29 29.5 UL-94 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 Totalpackage FR 1.90% 1.50% 1.50% 1.50% 0.80% 0.75% 0.75% 0.75% additives

Table 5 shows the FR activity of some of the flame retardantcompositions obtained according to the process of the invention,compared with two comparative compositions reported in the state of theart. In particular, solely by way of comparison, formulations wereconsidered comprising only one of the two types of bromine present inthe formulation of the invention, suitably formulated. The comparativecomposition 1 comprises only melamine bromohydrate without the complex,while the comparative composition 2 comprises only the ML/BiBr3 complexwithout melamine bromohydrate.

In the case in point, apart from the flame retardant effectivenesssubstantially similar or slightly higher in some cases, the flameretardant compositions obtained according to the process of theinvention show excellent FR activity even when they are simply added tothe polymer in the presence of the radicals promoter (CCPIB), while manyof the FR compositions of the prior art require the addition of othersynergists.

The invention permits numerous advantages to be achieved, in partalready described.

The preparation process of a flame retardant composition made fromhalogenated bismuth and/or antimony compounds complexed with melamineaccording to the invention is applicable industrially more simply thanthe current processes.

In particular, the process according to the invention is more easilycontrollable to avoid degradation of the active compounds, without theneed for direct control of the exothermy of the reactions.

Thanks to the presence of a reaction carrier which is not involved inthe reactions and acts as a support for said reactions, the processaccording to the invention makes it possible to easily control theaggressiveness of the reagents, intermediates and reaction products.This has a positive effect on the life of the plant.

The process according to the invention makes it possible to prepareflame retardant compositions containing complexes of melamine andbromides of antimony or bismuth, avoiding the handling—outside thereactor—of metal bromides, unstable and dangerous substances.

The process according to the invention makes it possible to obtain aflame retardant composition made from brominated compounds of bismuthand/or of antimony complexed with melamine in a pure form, free ofpolymeric matrices, and thus utilisable as a general purpose activeprinciple.

The process according to the invention makes it possible to obtain flameretardant compositions made from brominated compounds of bismuth and/orof antimony complexed with melamine with properties of chemicalstability and limited aggressiveness, and thus easier to manipulate.

The invention thus conceived thereby achieves the intended objectives.

Obviously, its practical embodiments may assume forms and configurationsdifferent from those described while remaining within the scope ofprotection of the invention.

What is claimed is:
 1. Flame retardant composition, characterized inthat it is composed of: a complex having a formula ML(MeBr₃), where MLindicates melamine and Me is bismuth or antimony; melamine bromohydrate;at least one among the compounds chosen from the group consisting ofmelamine, melamine phosphate, melamine polyphosphate, ammoniumphosphate, ammonium polyphosphate, graphite, silica, lignin,triphenyl-phosphate, coke and compounds containing triazine ringscondensed or linked by —NH groups; and optional additives; wherein thecomposition is composed of: 20-65% in weight of said complex having theformula ML (MeBr₃); 20-65% in weight of melamine bromohydrate; 10-40% inweight of at least one among the compounds chosen from the groupconsisting of melamine, melamine phosphate, melamine polyphosphate,ammonium phosphate, ammonium polyphosphate, graphite, silica, lignin,triphenyl-phosphate, coke and compounds containing triazine ringscondensed or linked by —NH groups; 0-3% of additives.
 2. Flame retardantcomposition, characterized in that it is composed of: a complex having aformula ML(MeBr₃), where ML indicates melamine and Me is bismuth orantimony; melamine bromohydrate; at least one among the compounds chosenfrom the group consisting of melamine, melamine phosphate, melaminepolyphosphate, ammonium phosphate, ammonium polyphosphate, graphite,silica, lignin, triphenyl-phosphate, coke and compounds containingtriazine rings condensed or linked by —NH groups; and optionaladditives; wherein the composition is composed of: 25-35% in weight ofsaid complex having the formula ML (MeBr₃); 25-35% in weight of melaminebromohydrate; 25-35% in weight of at least one among the compoundschosen from the group consisting of melamine, melamine phosphate,melamine polyphosphate, ammonium phosphate, ammonium polyphosphate,graphite, silica, lignin, triphenyl-phosphate, coke and compoundscontaining triazine rings condensed or linked by —NH groups; 0-3% ofadditives.
 3. Flame retardant composition, characterized in that it iscomposed of: a complex having a formula ML(MeBr₃), where ML indicatesmelamine and Me is bismuth or antimony; melamine bromohydrate; at leastone among the compounds chosen from the group consisting of melamine,melamine phosphate, melamine polyphosphate, ammonium phosphate, ammoniumpolyphosphate, graphite, silica, lignin, triphenyl-phosphate, coke andcompounds containing triazine rings condensed or linked by —NH groups;and optional additives; wherein the composition is, composed of: 55-65%in weight of said complex having the formula ML (MeBr₃); 20-25% inweight of melamine bromohydrate; 10-20% in weight of at least one amongthe compounds chosen from the group consisting of melamine, melaminephosphate, melamine polyphosphate, ammonium phosphate, ammoniumpolyphosphate, graphite, silica, lignin, triphenyl-phosphate, coke andcompounds containing triazine rings condensed or linked by —NH groups;0-3% of additives.
 4. Flame retardant composition, characterized in thatit is composed of: a complex having a formula ML(MeBr₃), where MLindicates melamine and Me is bismuth or antimony; melamine bromohydrate;at least one among the compounds chosen from the group consisting ofmelamine, melamine phosphate, melamine polyphosphate, ammoniumphosphate, ammonium polyphosphate, graphite, silica, lignin,triphenyl-phosphate, coke and compounds containing triazine ringscondensed or linked by —NH groups; and optional additives; wherein thecomposition is composed of: 20-25% in weight of said complex having theformula ML (MeBr₃); 55-65% in weight of melamine bromohydrate; 10-20% inweight of at least one among the compounds chosen from the groupconsisting of melamine, melamine phosphate, melamine polyphosphate,ammonium phosphate, ammonium polyphosphate, graphite, silica, lignin,triphenyl-phosphate, coke and compounds containing triazine ringscondensed or linked by —NH groups; 0-3% of additives.
 5. Compositionaccording to claim 1, in the form of dry powder, with mean particle sizebetween 5 μm 50 μm.
 6. Composition according to claim 2, in the form ofdry powder, with mean particle size between 5 μm 50 μm.
 7. Compositionaccording to claim 3, in the form of dry powder, with mean particle sizebetween 5 μm-50 μm.
 8. Composition according to claim 4, in the form ofdry powder, with mean particle size between 5 μm-50 μm.